In principle, a great variety of different individual technical solutions are known as active or also as passive braking systems for shutter drives. Shutter drives with active electromagnetic or electromechanical brakes consume additional energy and generate considerable switching noise when actuated. Furthermore, they also need a relatively large mounting space as can be seen, e.g. from EP 000 0002 234 245 and DE 20 2005 007 921. The advantage of passively acting braking systems is that they need no auxiliary energy and occupy a smaller mounting space.
DE 10 2005 047 296 B3 describes a centrifugal brake having a brake drum that surrounds the rotating element at least partially and at least one centrifugal block which is disposed on the rotating element and is substantially radially movable between the rotating element and an inner wall of the brake drum. An additional braking device is provided for actuation when the rotating element exceeds a predefined speed. This makes it possible to bring the rotating element rapidly to a standstill. Generally, such brakes are not used for stopping a rotational speed strongly or even rigidly, but only for limiting it. From a defined rotational speed, the centrifugal blocks start moving radially outwards from their rest position as a result of the centrifugal force acting on them. When a defined actuating speed is reached, the centrifugal blocks come in contact with the brake drum so that friction and, related to this, a braking effect occurs. In specific application cases the brake drums are also used to stop the rotating element.
From U.S. Pat. No. 4,216,848 a braking device for a rod-like element is known, where centrifugal blocks can be brought in contact with a so-called brake shoe to cause it to rotate and move axially towards the rod. During this, a brake wheel is pushed against a brake disc, finally braking the rod-like element.
DE 10 2015 106 833 A1 describes a centrifugal brake for shutter drives, having two spring elements which apply a holding force in addition to a braking force. This centrifugal brake is coupled to a drive shaft of the shutter drive and is actuated by the shutter drive motor. It is constructed to act inversely, i.e. not braking as known, but locking and decoupling on start-up. It has a turntable coupled with the shutter drive shaft via a shaft flange. Two or more centrifugal blocks are disposed and slidably guided in the turntable. When the shutter drive is in a de-energized state, the centrifugal blocks with their partially overarching brake blocks engage, frictionally or positively locking, with the surface of a friction ring that is fixedly disposed at the motor housing frame. When the drive motor starts, the brake blocks are released, i.e. disengaged. The radial distance of the brake blocks is maintained until the current is switched off and the drive motor 11 comes to a standstill. Then the centrifugal blocks with the angled brake blocks are radially pulled inside, acting as a reliable lock. The spring elements are dimensioned such that the brake blocks provide a sufficient holding torque. However, problems of wear may occur when they are frequently actuated.
Furthermore, DE 93 13 666.8 U1 describes a braking device for an electric motor, in particular a tubular electric motor provided with a purely mechanical brake with at least one brake pad, brake blocks and elastic means. When the brake is at rest, the brake blocks are pushed against a brake pad, using spring force. The brake is provided with flyweights which move the elastic means out of their braking position under the influence of the centrifugal force. At rest (de-energized), this brake is active, and when the electric motor starts, the brake is released by the action of centrifugal force. The brake blocks are specifically configured in the form of crown segments which are hinged at one end to a brake block carrier. The elastic means used are arc-shaped springs. This braking device as a frictional blocking brake is constructively relatively long in the axial direction and therefore requires considerable mounting space.